I have come to the conclusion I don't like the phrase "science communicator". You would think that it goes without saying that all scientists must communicate their work, for what is the point of learning new things about how the world works if you don't tell anyone about them?

But, alas, the term seems to be reserved only for that small minority of scientists - increasing though its numbers have been in recent years - who recognise the importance of sharing their theories and observations with more than just the dozen researchers around the world who bother to read their highly specialised journal papers. An even smaller minority, though - and I brazenly include myself - don't so much stick their heads shyly over the parapets of their ivory towers to peer out at the big wide world as jump out on to the ledge with a loudspeaker. But a question I wish to address here is one that does not receive a universal answer. Should these science explainers restrict themselves in their public utterances to their own subject, or are they right to join in with other social commentators in the public arena to opine on wider societal issues such as ethics or faith?

Which brings me to my reason for writing this piece. Richard Dawkins, that less than shy champion of militant atheism, stepped down recently from his famous Charles Simonyi chair in science communication at Oxford. His successor is the youthful professor of mathematics Marcus du Sautoy. This is a great appointment, as Du Sautoy is already doing the sort of things this chair was created for. But Dawkins's stature and reputation have raised the profile of the Simonyi chair, making it a platform for utterances that are hugely magnified in their reach and influence. In a way it is similar to what Stephen Hawking has brought to the Lucasian chair of mathematics at Cambridge - from which he retires next year - despite previous holders including the likes of Isaac Newton.

Of course, Du Sautoy will not, and probably should not, need to change what he does in his new role. He is already a successful broadcaster and author as well as a serious academic. And I certainly do not intend to offer him advice on the path he should take. But whether or not one agrees with Dawkins's confrontational, firebrand style, there is no denying that he has made moderate atheism - that which tries hard not to insult those of faith by trivialising what they hold dear - respectable.

By positioning himself on one extreme, Dawkins has allowed this cuddlier atheist to occupy the centre ground. It is rather like the political spectrum of the latter half of the last century, when communism provided the buffer and excuse for the respectability of socialism. Today's world is very different, and with communism discredited, those of us who proudly labelled ourselves socialists in Thatcherite Britain now feel safer being re-branded as liberals with socialism the new extreme of the left.

I do feel strongly however that those scientists who have a voice must be doing more than simply popularising their field to attract the next generation into science. Yes, this is vital; but it is also vital that we help defend our rational, secular society against the rising tide of irrationalism and ignorance. Science communicators, for want of a better term for now, have a role to play in explaining not just the scientific facts but how science itself works: that it is not just "another way of viewing the world"; and that without it we would still be living in the dark ages.

I do not mean that everyone should become an expert in quantum mechanics (although wouldn't that be great). But when there are so many people (such as the thankfully defeated Republican vice-presidential candidate in the US) who truly believe that dinosaurs roamed the earth at the same time as humans, or that the universe itself was created six thousand years ago - or who spend millions of pounds on homeopathic remedies or magic crystals instead of real medicine - then we scientists simply cannot hide away in our labs.

I have recently been involved in making a BBC series on medieval science in the early Islamic empire. While we marvel at the contributions to mathematics, astronomy and medicine that these scholars made a millennium ago, we tend to scoff at the more naive notions they entertained in folklore, astrology or alchemy - until we remember that they wouldn't look so out of place in 21st-century Europe or America.

Science communicators are therefore more than just cheap popularisers providing soundbites for a public hungry to know what subatomic exotica will be conjured into existence at the Large Hadron Collider. They have a huge role to play in keeping the light of rationalism shining brightly. Love him or loathe him, Dawkins has played his part in this.

• Jim Al-Khalili is professor of physics and professor of the public engagement in science at the University of Surrey j.al-khalili@surrey.ac.uk